A synovial hemangioma in the knee joint of a 13-year old woman was diagnosed and removed arthroscopically. Synovial hemangioma is a rare, benign lesion affeting children and young adults. The lesion most commonly affects the knee joint. A recurrent history of pain and swelling is a charateristic feature, the degree of pain and tenderness can vary from mild to excruciating. Quadriceps atrophy and limitation of motion are other features. At arthroscopy, a 13-year old woman with repeated spontaneous hemarthrosis of the knee was found to have a synovial hemangioma, which was removed arthoscopically.